Abstract
Since 1990 Maribo Seed has conducted field trials with transgenic sugarbeet. Glyphosate tolerance has been the main objective. Trials are performed in Denmark, France, England, and Belgium, and in 1993 for the first time in USA. As sugarbeet varieties are hybrids, the transformation can be made on either multigerm, diploid fatherJines or monogerm, diploid motherJines (CMS-lines). Our development work has involved a range of different genetical constructs from Monsanto. The Agrobacterium vector transfers the insert into random chromosomal positions in single or multiple copies. Transformed plants are cloned to about 10 copies each and tested. If the GUS gene is present, GUS analysis on pollen can distinguish between plants which are homozygous and heterozygous for the introduced traits. Transgenic beets, but also progenies of transgenic beets, show considerable variation in the expression of the genes inserted (position effects). We have seen indications of interactions between transgenes and native genes. In most cases transgenes segregate according to Mendel's laws. The occurrence of meiotic irregularities, chimerics and multi-copy inserts can add to the complexity of developing transgenic lines, but classical breeding techniques are able to select Jines which are identical to the parental line except for the introduced trait.
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